What is any plant of the natural order Elatineæ, consisting of two genera (Elatine, and Bergia), mostly small annual herbs growing in the edges of ponds. Some have a peppery or acrid taste called?

waterwort — Any plant of the natural order Elatineæ, consisting of two genera (Elatine, and Bergia), mostly small annual herbs growing in the edges of ponds. Some have a peppery or acrid taste. (Webster's 1913.)

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